Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well known in the art and typically involve use of a guide wire and a balloon catheter, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached to its distal end and a manifold attached to the proximal end. In use, the balloon catheter is advanced over the guide wire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened.
Vascular restrictions that have been dilated do not always remain open. In approximately 30 to 50% of the cases, a restriction reappears over a period of months. The mechanism of this restenosis is not understood. The mechanism is believed to be different from the mechanism that caused the original stenosis. It is believed that rapid proliferation of vascular smooth muscle cells surrounding the dilated region may be involved. Restenosis may be in part a healing response to the dilation, including the formation of scar tissue.
Intravascular radiation, including thermal, light and radioactive radiation, has been proposed as a means to prevent or reduce the effects of restenosis. For example, U.S. Pat. No. 4,799,479 to Spears suggests that heating a dilated restriction may prevent gradual restenosis at the dilation site. In addition, U.S. Pat. No. 5,417,653 to Sahota et al. suggests that delivering relatively low energy light, following dilatation of a stenosis, may inhibit restenosis. While most clinical studies suggest that thermal radiation and light radiation are not significantly effective in reducing restenosis, some clinical studies have indicated that intravascular delivery of radioactive radiation is a promising solution to the restenosis enigma.
Delivery of radioactive radiation have been proposed as a means to prevent or reduce the effects of restenosis. For example, U.S. Pat. No. 5,199,939 to Dake et al. suggests that intravascular delivery of radiation may inhibit restenosis. Dake et al. suggest delivering radiation within the distal portion of a tubular catheter. Use of radioactive pellets, or, alternatively, liquid gas or powder, is also suggested. Fischell, in the publication EPO 0 593 136 A1, suggests placing a thin wire having a radioactive tip near the site of vessel wall trauma for a limited time to prevent restenosis.
Since radioactive radiation prevents restenosis but will not dilate a stenosis, radiation is preferably administered during or after dilatation. European Patent No. 0 688 580 to Verin discloses a device and method for simultaneously dilating a stenosis and delivering radioactive radiation. In particular, Verin '580 discloses a balloon dilatation catheter having an open-ended lumen extending therethrough for the delivery of a radioactive guide wire.
Other methods of providing radiation to treatment sites have been proposed. Thornton et al., in the PCT publication WO 96/17654 describe an inflatable treatment balloon which is inflated with a liquid containing suspended radioactive materials such as I.sub.125 or P.sub.32. Walker et al., in PCT publication WO 96/13303, suggest forcing radioactive capsules or pellets through a catheter using fluid pressure to arrive at the treatment site.
What would be desirable is a non-wire based, non-hydraulic, non-pneumatic device providing simple, rapid and controlled delivery and withdrawal of radiation to a treatment site within the human body. A radioactive device allowing use and re-use without sterilization would be desirable.